KR20020058058A - Process for producing enlarged latex - Google Patents

Abstract

A process for preparing an enlarged latex, which comprises (1) causing (a) an anionic surfactant and (b) at least one surfactant selected from the group consisting of a cationic surfactant and an amphoteric surfactant to exist in a latex, (2) adding, as an aggregating and enlarging agent, at least one selected from the group consisting of (i) an inorganic acid, (ii) an organic acid, (iii) a substance which forms an acid in water, (iv) a combination of at least two substances which are reacted with each other to form an acid, and (v) a substance which forms an acid by exposure to active rays to the latex in the presence of these surfactants, and (3) causing the acid derived from the aggregating and enlarging agent to act on the latex, thereby enlarging the particle diameter of the latex, an enlarged latex obtained by the preparation process, a graft copolymer obtained by polymerizing a polymerizable monomer with the enlarged latex, and a resin composition comprising the graft copolymer and a thermoplastic resin.

Description

How to make enlarged latex {PROCESS FOR PRODUCING ENLARGED LATEX}

Latex is an emulsion in which polymers such as rubber or plastics are dispersed in water in the form of colloids by emulsifiers. As a synthetic latex, For example, rubber latex, such as styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, and polychloroprene rubber latex; And resin latexes such as vinyl acetate (co) polymer latex, styrene (co) polymer latex, and acrylic ester (co) polymer latex are prepared by emulsion polymerization. Latexes are used in a wide variety of applications, such as in the field of synthetic resins, in paints, in the treatment of paper and textiles, and in civil engineering such as concrete and asphalt.

Latexes are generally emulsions in which polymers with fine particle diameters are dispersed. However, latexes with larger particle diameters are required in many applications because they are necessary for the desired final application. Graft copolymers obtained by polymerizing vinyl monomers in the presence of rubber latex are used as impact modifiers for thermoplastics and the like. Of these graft copolymers, those having various particle diameters are selected for use because they are needed for the desired final application. Latexes with large particle diameters are preferably used to obtain graft copolymers with large particle diameters.

Latexes are generally produced by emulsion polymerization methods. However, it takes a long polymerization time to obtain latex having a large particle diameter by the seed crystal polymerization method, which results in lower productivity. In particular, when a diene monomer or a monomer mixture comprising a diene monomer and a vinyl monomer is polymerized by the seed crystal polymerization method to obtain a latex having a large particle diameter, a very long polymerization time is required. A method for obtaining a latex having a large particle diameter in a short time, in which inorganic acids, organic acids, salts, flocculants and / or latexes for enlarging have a small particle diameter in order to enlarge the latex by aggregation. A method of adding to latex has been proposed.

For example, Japanese Patent Application Laid-Open No. 71603/1997 discloses that rubber masses are not produced in diene polymer rubber latex obtained by emulsion polymerization in order to facilitate the mixing of flocculant while expanding latex by flocculation, mainly brown flocculation. We propose a method in which a gentle shear is applied. Brown agglomeration means that the latex particles undergo Brownian motion and thereby collide with each other to agglomerate. More specifically, the method involves lowering the number of revolutions upon agitation, in expanding the latex by flocculation using a flocculant, mainly to effect flocculation by Brownian motion, thereby resulting in the formation of agglomerated masses. Interfere to enlarge latex by flocculation. This method uses a combination of shear agglomeration and brown agglomeration with a stirring blade. According to this method, the latex particles can be expanded to a certain degree. However, judging by the embodiment, the particles cannot be enlarged to a sufficient degree. In addition, in this method, an acid is used as a flocculant, and a flocculant is added to maintain the pH of the system below 5. However, in order to stabilize the latex, when trying to raise the pH of the system by adding a base substance to the expanded latex obtained by this method, the stability of the latex becomes insufficient due to the high salt concentration in the system. Thus, when graft polymerization of vinyl monomers is attempted in the presence of the latex, a problem arises in that precipitates are easily formed.

Japanese Patent Publication No. 2229/1969 discloses a method for enlarging particles by adding a monomer to the dispersion to allow graft polymerization to proceed, while adding formaldehyde sulfoxylate and peroxide to an aqueous dispersion comprising fine particles of butadiene polymer. Suggested. However, according to this method, it is difficult to expand the particles to a sufficient degree.

Japanese Patent Application Laid-Open No. 45921/1981 discloses adding an acrylic ester-unsaturated acid copolymer latex obtained by polymerization in the presence of an anionic surfactant and having a pH of 4 or more to a synthetic rubber latex having a pH adjusted to 7 or more, Therefore, a method of enlarging the particle diameter of the synthetic rubber latex has been proposed. However, according to this method, there is a need to separate and prepare latex for expansion. Thus, this method is undesirable in terms of complexity and economy in operation. Additionally, in the presence of synthetic rubber latex expanded by adding such acrylic ester-unsaturated acid copolymer latex, when attempting to graft polymerization of vinyl monomers, the stability of the latex is impaired to form agglomerated mass. .

Disclosure of the Invention

It is an object of the present invention to provide a method for producing enlarged latex, which method is economical and productive and which allows to expand the latex while retaining the stability of the latex.

It is another object of the present invention to provide a method for producing expanded latex, wherein the stability of the latex is not impaired even when the polymerizable monomer is graft polymerized in the presence of the expanded latex.

It is a further object of the present invention to expand latex having such excellent various properties, to prepare a graft copolymer by polymerizing a polymerizable monomer in the presence of the expanded latex, a resin composition comprising a graft copolymer and a thermoplastic resin, and It is to provide a graft copolymer (latex, slurry or particles) with a uniform particle diameter distribution.

The present invention has undergone extensive investigation to achieve the above object. As a result, anionic surfactants and cationic surfactants and / or amphoteric surfactants are present in the latex and acids or acids capable of forming acids can be added to the flocculating and expanding agent, thereby reducing the It was devised to enlarge the particle diameter.

When the pH of the latex stabilized by the anionic surfactant is lowered by acid, the initial particles of the latex aggregate and expand. However, the stabilizing effect by the anionic surfactant is weakened when the pH is lowered, and as a result, the stability of the latex tends to be impaired. On the other hand, when anionic surfactants and cationic surfactants and / or amphoteric surfactants are present in the latex, (1) the system is stable due to the stabilizing effect by the anionic surfactants when the pH is high, (2 Stabilization effect by anionic surfactants is weakened when the pH is lowered by acid, resulting in agglomeration and enlargement of latex particles, and (3) lower pHs further cationic surfactants and / or amphoteric surfactants. The stabilization effect by the activator stabilizes the system again. As a result, stabilized expanded latex can be obtained. Even when stabilized expanded latex is used in the graft polymerization reaction, the stability of the system is not impaired.

In this method, the pH is lowered by using a combination of two or more substances which react with each other to form an acid, for example, a combination of hydrogen peroxide and formaldehyde sulfoxylate, and brown agglomeration without stirring during expansion by aggregation. In the case where expansion by aggregation is carried out by the expansion, expansion latex having a narrow particle diameter distribution and a large particle diameter can be stably formed.

Graft copolymers obtained by graft polymerization of polymerizable monomers on expanded latex obtained by the process according to the invention can be used in a wide variety of applications per se and also exhibit excellent properties as impact modifiers for thermoplastics. The present invention has been completed based on this finding.

According to the present invention there is provided a method of making enlarged latex by enlarging the latex by flocculation, which comprises:

(1) (a) anionic surfactants and

(b) at least one surfactant selected from the group consisting of cationic surfactants and amphoteric surfactants is present in the latex,

(2) adding at least one selected from the group consisting of to the latex in the presence of the surfactant as a flocculating and expanding agent,

(Iii) inorganic acids,

(Ii) organic acids,

(Iii) substances that form acids in water,

(Iii) a combination of two or more substances that react with each other to form an acid, and

(Iii) a substance that forms an acid by exposure to active radiation,

(3) The acid derived from the flocculating and expanding agent is allowed to act on the latex, thereby expanding the particle diameter of the latex.

According to the invention, there is also provided an enlarged latex obtained by the above production method. According to the present invention, there is further provided a method for producing a graft copolymer comprising polymerization of a monomer which can be polymerized in the presence of the expanded latex, and a resin composition containing the graft copolymer and the thermoplastic resin obtained by the method. Is provided.

According to the invention, it comprises an anionic surfactant and at least one surfactant selected from the group consisting of cationic surfactants and amphoteric surfactants, wherein the volume average particle diameter (Dv) vs. number average particle diameter of 1.2 to 1.8 ( Also provided are graft copolymers having a ratio of Dn) (Dv / Dn).

Best way to carry out the invention

1.Latex :

The latex used in the present invention can be produced by any method. However, latex synthesized by emulsion polymerization is generally used. No special limitation is imposed on the component producing the latex. However, examples thereof include (co) polymers of diene monomers such as butadiene, isoprene and chloroprene; (Co) polymers of vinyl monomers such as styrene, acrylonitrile, acrylic esters, methacryl esters, ethylene, vinyl chloride, vinylidene chloride, vinyl acetate and vinyl fluoride; Copolymers of diene monomers and vinyl monomers; Silicone resins such as polyorganosiloxanes; And polyesters, epoxy resins, melamine resins, polyamides and polyurethanes. Such polymers may be used alone or in any combination thereof. The latex may have a structure such as a core / shell structure and may be an organic / inorganic composite latex.

In order to control the expansion by aggregation by controlling the surface charge of the latex, latexes obtained by copolymerizing the diene monomer and / or the vinyl monomer with monomers having anionic and / or cationic functional groups may also be used. Examples of monomers having functional groups are acrylic acid, methacrylic acid, itaconic acid, fumaric acid, acrylamide, methacrylamide, hydroxyethyl methacrylate, hydroxyethyl acrylate and glycidyl methacrylate. In addition, crosslinkable monomers such as divinylbenzene, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate or 1,3-butanediol diacrylate can be used in combination.

In the polymerization of latex, a radical polymerization initiator, a thermally decomposable polymerization initiator, an oxidation-reduction initiator, or the like can be used. In addition, light, X-rays and the like can also be used. Chain transfer agents, such as t-dodecyl mercaptan, n-octyl mercaptan or α-methylstyrene dimer, may be used as necessary during the polymerization. Surfactants are used in the polymerization. However, this will be described later.

These latexes can be used alone or in any combination thereof. Of these, (co) polymer latexes of diene monomers, (co) polymer latexes of vinyl monomers, or copolymer latexes of diene monomers and vinyl monomers are preferred. When the process according to the invention is applied to diene (co) polymer latexes comprising diene monomers such as butadiene, good effects are achieved, particularly in terms of shortening the polymerization time.

Examples of diene (co) polymer latexes include (co) polymer latexes of diene monomers such as butadiene, isoprene and chloroprene; And copolymer latexes of diene monomers and vinyl monomers. Examples of vinyl monomers that can be copolymerized with diene monomers include aromatic vinyl monomers such as styrene and α-methylstyrene; Alkyl (meth) acrylates such as methyl methacrylate and n-butyl acrylate; And unsaturated nitrile monomers such as acrylonitrile. Examples of (co) polymer latexes of diene monomers include polybutadiene latex. Examples of diene copolymers include copolymer rubbers of diene monomers such as butadiene and vinyl monomers such as styrene. No particular limitation is imposed on the copolymerization ratio of diene monomer to vinyl monomer. However, for example, copolymers of 50 to 99% by weight of diene monomers and 1 to 50% by weight of vinyl monomers can be mentioned.

No particular limitation is imposed on the particle diameter (volume average particle diameter) of the latex. However, 200 nm or less is preferable, and 150 nm or less is more preferable because latex having a fine particle diameter of 150 nm or less, further 100 nm or less, can be effectively enlarged by the method according to the present invention.

2. Surfactant :

In the present invention, at least one surfactant selected from the group consisting of (a) anionic surfactants and (b) cationic surfactants and amphoteric surfactants is present in the latex. As an example of a method for ensuring that such surfactants are present in the latex, during polymerization of the latex, emulsion polymerization is performed with anionic surfactants, and then cationic surfactants and / or amphoteric surfactants are added to the resulting latex. The method is mentioned. However, when cationic surfactants and / or amphoteric surfactants are added to the latex comprising anionic surfactants, in some cases precipitates may be produced. In this case, in the production of latex, a method in which cationic surfactants and / or amphoteric surfactants are previously added together with anionic surfactants is preferred. In order to prevent the formation of precipitates, polymerization is carried out with anionic surfactants and cationic surfactants and / or both with cationic surfactants and / or amphoteric surfactants mixed with excess anionic surfactants. Methods of adding the surfactant during the polymerization or after the polymerization may also be adopted.

As examples of the anionic surfactants, those conventionally used in emulsion polymerization such as carboxylic acid salts, sulfonic acid salts, sulfuric acid ester salts and phosphate ester salts may be mentioned. Among these, carboxylate type surfactants such as sodium oleate, potassium oleate, sodium stearate, potassium stearate, sodium myristate, potassium myristate, sodium palmitate, potassium palmitate, lauric Alkali metal salts of higher fatty acids such as potassium acid, potassium undecanoate, sodium linoleate, potassium linoleate, potassium caprylate, potassium nonanoate and potassium capricate; Alkali metal salts of rosin acid, such as disproportionating potassium rosinate; Alkali metal salts of alkyl sarcosine acids; And alkali metal salts of alkenyl succinic acid. These anionic surfactants can be used alone or in any combination. When carboxylate type anionic surfactants are used, sulfonate type anionic surfactants and nonionic surfactants can be used in combination as an adjuvant.

Examples of cationic surfactants include quaternary ammonium salts with one or more alkyl groups, primary to tertiary amine salts with one or more alkyl groups, alkylphosphonium salts and alkylsulfonium salts. More specifically, for example, benzalkonium chloride, alkyltrimethylammonium chloride, alkylamine acetate, alkylamine hydrochloride, dialkyldimethylammonium chloride, alkylisoquinolinium chloride and alkylisoquinolinium bromide May be mentioned.

Examples of amphoteric surfactants include N-octylbetaine, N-decylbetaine, N-undecylbetaine, N-dodecylbetaine, N-tetradecylbetaine, N-hexadecylbetaine, octylbetaine Betaines such as decylbetaine and dodecylbetaine; Carboxylic acid type amphoteric surfactants including betaines such as sulfobetaines or sulfatebetaines; Sulfate type amphoteric surfactants such as hydroxyethylimidazoline sulfate; Sulfonic acid type amphoteric surfactants such as imidazolinesulfonic acid may be mentioned.

Surfactants selected from the group consisting of cationic surfactants and amphoteric surfactants can be used alone or in any combination thereof. No particular limitation is imposed on the use ratio of (a) anionic surfactant to (b) cationic surfactant and / or amphoteric surfactant. However, in terms of stability of the latex, control of expansion by aggregation and stability of the expansion latex, (a) per 100 moles of anionic surfactant (b) cationic surfactant and / or amphoteric surfactant is preferably 0.01 to 100 Molar, more preferably from 0.1 to 80 moles, even more preferably from 1 to 50 moles. Surfactants are generally used in a ratio of 0.1 to 5 total parts per 100 parts by weight of the (co) polymer component in the monomer (s) or latex forming the (co) polymer component.

3. flocculating and expanding agent:

In the present invention, (i) an inorganic acid, (ii) an organic acid, (i) a substance that forms an acid in water, (iii) a combination of two or more substances that react with each other to form an acid, and (iii) exposure to active radiation And at least one selected from the group consisting of substances which form acids by means of flocculating and expanding agents.

As examples of inorganic acids, mention may be made of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid. As examples of organic acids, acetic acid, formic acid, tartaric acid, malic acid and butyric acid may be mentioned. Examples of the substance which forms an acid in water include acid anhydrides such as acetic anhydride and maleic anhydride; Esters such as sulfuric acid esters and phosphoric acid esters may be mentioned.

As a combination of two or more substances which react with each other to form an acid, a combination of substances which form an acid by an oxidation-reduction reaction is preferable, and specific examples thereof are peroxide / formaldehyde, peroxide / sulfoxylate and peroxide / formaldehyde Sulfoxylate combinations. Of these, peroxide / formaldehyde sulfoxylate (for example, sodium formaldehyde sulfoxylate) combination is preferred.

As for the substance which forms an acid by exposure to actinic radiation, no special limitation is added as long as it is a substance which forms Bronsted acid or Lewis acid by exposure to actinic radiation. Specific examples thereof include onium salts, halogenated organic compounds, quinonediazide compounds, α, α-bis (sulfonyl) diazomethane compounds, α-carbonyl-α-sulfonyl-diazomethane compounds, sulfone compounds, organic esters Compounds, organic acid amide compounds, and organic acid imide compounds. Examples of actinic radiation include ultraviolet rays, far ultraviolet rays, electron beams and laser beams.

These acids and acid forming materials are generally added to the latex in the form of aqueous solutions. As for the added amount, since the acidity varies depending on the acid or the type of acid-forming substance, it is preferable that the amount of latex is easily achieved within the range confirmed by the experiment that no aggregated mass of latex is formed. Do. Preferred experimental examples in this regard are specifically shown in the respective examples.

In order to adjust the particle diameter of the magnifying latex, a flocculating and expanding agent and a salt can be used in combination. The salt may be included in latex in advance or may be added prior to the expansion treatment by flocculation. Examples of salts that do not have a pH buffering effect include sodium chloride, potassium chloride and calcium chloride. Examples of salts having a pH buffering effect include sodium pyrophosphate, sodium carbonate and ammonium sulfate.

4. Magnification Processing :

In the present invention, the acid derived from the flocculating and expanding agent acts on the latex, thereby expanding the particle diameter of the latex. More specifically, anionic surfactants and cationic surfactants and / or amphoteric surfactants are present in the latex and the acid or acid forming material is added to the latex as a flocculating and expanding agent and thus derived from the flocculating and expanding agent. Allow the acid to act on the latex. If the flocculating and expanding agent is a substance which forms an acid in the inorganic acid, the organic acid or the water, the acid immediately performs the flocculating and expanding action in the latex.

When the flocculating and expanding agent is a combination of two or more substances that react with each other to form an acid, a chemical reaction between these substances takes place in latex to form an acid, which acid performs the flocculating and expanding action. When the flocculating and expanding agent is a substance which forms an acid by exposure to actinic radiation, the latex is exposed to actinic radiation to form an acid, and thus, the formed acid performs an agglomeration and expanding action.

In order to enhance the magnification effect in the magnification process by aggregation, ultrasonic vibrations can be applied. No special limitation is imposed on the treatment temperature upon expansion by aggregation. However, 20 to 90 ° C, which is a temperature that is easy to control, is preferable, and a temperature that is higher than the glass transition temperature of the polymer component forming the latex is more preferable.

The expansion treatment by aggregation may be performed while stirring the latex. However, the agitation can stop after the flocculation and addition of the expanding agent, and the agitation and mixing are performed lightly to disperse uniformly. If agitation of the latex is not performed, the expansion of the latex is caused by brown aggregation of the latex particles. When the flocculating and expanding agent is a combination of two or more substances which form an acid to react with each other or a substance which forms an acid by exposure to active radiation, the brown flocculation is performed without stirring the latex in the step of causing the acid to act on the latex. The method for enlarging the latex by means of the aspect of providing an enlarged latex having a narrow particle diameter distribution expressed by the ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn). In this case, the formation of acid in the system and the brown aggregation by the action of the acid are advanced in a well controlled relationship, resulting in the formation of a uniformly expanded latex with a narrow particle diameter distribution. Latex uniformly enlarged with a narrow particle diameter distribution shows high quality and high performance in the various applications in which it is used.

After expanding the latex, base materials such as sodium hydroxide, potassium hydroxide, sodium carbonate or potassium carbonate are generally added to the latex to neutralize the acid. Such base materials are generally added to the latex in the form of an aqueous solution.

No particular limitation is imposed on the particle diameter of the expanding latex. However, it is generally about 200 to 1,000 nm or more, preferably in terms of its volume average particle diameter (Dv). Even when the method according to the invention is applied to latex having a fine particle diameter, the latex can be enlarged to a volume average particle diameter of preferably at least 200 nm, more preferably at least 250 nm. The latex can be expanded to 300 nm or more and additionally 350 nm or more as necessary. In particular, when the volume average particle diameter is expanded to 300 nm or more, the effect of the present invention is remarkable. No particular limitation is imposed on the particle diameter distribution (Dv / Dn) of the expanding latex. However, according to the present invention, in terms of Dv / Dn, an enlarged latex having a uniform particle diameter of preferably 1.2 to 1.8, more preferably 1.2 to 1.6, even more preferably 1.2 to 1.5 can be provided. .

5. Graft Polymerization and Graft Copolymers :

The expanded latex obtained by this method is graft polymerized, whereby a graft copolymer can be obtained. Graft polymerization can be carried out by polymerizing monomers which can be polymerized in the presence of expanded latex. No particular limitation is imposed on the graft polymerization process. However, emulsion polymerization methods and suspension polymerization methods are preferred. In graft polymerization, surfactants such as anionic surfactants, cationic surfactants, amphoteric surfactants or nonionic surfactants; Suspending agents such as organic suspending agents or inorganic suspending agents may be appropriately added to further stabilize the system. No particular limitation is imposed on the polymerizable monomers used in the graft polymerization. However, vinyl monomers are preferred. Also no particular limitation is imposed on the weight ratio of the expanded latex to the polymerizable monomer. However, they are preferably graft polymerized at a ratio of 5 to 95% by weight of solid latex and 95 to 5% by weight of vinyl monomer.

As an example of a vinyl monomer, Aromatic vinyl monomers, such as styrene and (alpha) -methylstyrene; Aromatic polycyclic vinyl monomers such as 4-vinyl biphenyl and 2-vinyl naphthalene; Unsaturated nitriles such as acrylonitrile and methacrylonitrile; Alkyl (meth) acrylate monomers such as methyl methacrylate and butyl acrylate; Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and maleic anhydride; And maleimide monomers such as maleimide and N-phenylmaleimide. These vinyl monomers may be used alone or in any combination thereof.

In the polymerization of vinyl monomers, polyfunctional vinyl monomers such as divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate or 1,3-butylene dimethacrylate may be suitably used in combination. Also, chain transfer agents such as t-dodecyl mercaptan or n-octyl mercaptan can be used.

Vinyl monomers that are graft polymerized on expanded latex can be added to the reaction system at one time, in several portions, continuously or in combination. If the graft polymerization is carried out in two or more stages, the monomer composition in each stage may be the same or different from each other.

When the graft polymerization is done in expanded latex by emulsion polymerization or suspension polymerization, a graft copolymer latex or slurry is provided comprising anionic surfactants and cationic surfactants and / or amphoteric surfactants. The ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn) in the graft copolymer according to the present invention is preferably 1.2 to 1.8, more preferably 1.2 to 1.6, even more preferred. Preferably 1.2 to 1.5, and the particle diameter thereof is uniform. However, in the graft copolymer obtained by performing graft polymerization by suspension polymerization, the particle diameter distribution of the grafted portion is often inconsistent with the particle diameter distribution of the graft copolymer. Therefore, the particle diameter distribution (Dv / Dn) of this graft copolymer is measured to indicate the ratio of volume average particle diameter to number average particle diameter (Dn) in the portion to be polymerized.

The transparency can be improved because the number of coarse particles is reduced by the narrow particle diameter distribution of the graft copolymer and the drop in transparency caused by scattering of light due to the coarse particles can be prevented. In addition, since the particles having a particle diameter effective for strengthening the strength are increased by the narrow particle diameter distribution of the graft copolymer, the strength is also enhanced. In particular, in view of transparency, the kind and combination of vinyl monomers to be grafted are preferably selected in such a manner that the refractive indices of the grafted polymer (enlarged latex particles) and the resulting graft copolymer coincide with each other. For example, when the expanded latex is butadiene rubber latex or styrene-butadiene rubber latex, styrene, methacrylic acid, butyl acrylate, and the like are suitably combined with vinyl monomers that are graft polymerized, resulting in the grafted polymer and the resulting graft The refractive indices of the copolymers can be matched to each other. It is preferred that the refractive index difference between the grafted polymer and the resulting graft copolymer is 0.02 or less.

The volume average particle diameter of the graft copolymer is generally at least 150 nm, preferably about 200 to 1,000 nm. In particular, when the volume average particle diameter is 300 nm or more, the effect by the application of the present invention is remarkable. However, as mentioned above, the volume average particle diameter of the graft copolymer obtained by carrying out the graft polymerization by suspension polymerization is measured to indicate the volume average particle diameter of the portion to be grafted.

After graft polymerization, the graft copolymer is provided as a latex, slurry or their separated and aggregated particles. From the latexes and slurries, no particular limitation is imposed on the method for separating and flocculating the graft copolymer into particles. As an example, however, a coagulant such as hydrochloric acid or calcium chloride is added to the latex to coagulate the particles, dewatering and drying the resulting slurry, and a method of spraying the latex into heated air to dry it. Can be. Either way, additives such as antioxidants, ultraviolet absorbers, anti-blocking agents, pigments, fillers, lubricants, antistatic agents and antibacterial agents may be suitably added before or after coagulation and drying. Graft copolymers can themselves be used as thermoplastics. In this case, the dry particles can be made as it is or pelletized, and then molded or formed and processed. No particular limitation is imposed on the forming or forming method. By way of example, conventional processing methods used for thermoplastics, such as calendering, extrusion, blow molding, and injection molding, can be employed.

6. Resin composition :

The graft copolymer according to the present invention may be mixed with a thermoplastic resin to prepare a resin composition. The mixing ratio between the two (based on the solid content) may be appropriately determined depending on the intended use and desired properties. In general, they may be appropriately selected in the range of 0.1 to 99.9% by weight of the graft copolymer and 99.9 to 0.1% by weight of the thermoplastic resin. In many cases, good results can be obtained at a ratio of 1 to 99% by weight of the graft copolymer and 99 to 1% by weight of the thermoplastic resin. When the graft copolymers are mixed with thermoplastic resins such as vinyl chloride resins as impact modifiers, they can often be mixed with each other in proportions of 1 to 50% by weight of the graft copolymer and 99 to 50% by weight of the thermoplastic resin.

No particular limitation is imposed on the thermoplastic resin. However, for example, polystyrene, high impact polystyrene (HI polystyrene resin), acrylic resin, methyl methacrylate styrene resin (MS resin), vinyl chloride resin, chlorinated vinyl chloride resin, acrylonitrile-styrene resin (AS Resins), acrylonitrile-butadiene-styrene resins (ABS resins), thermoplastic polyester resins and polycarbonate resins. Such thermoplastic resins may be used alone or in any combination thereof.

Additives such as antioxidants, ultraviolet absorbers, anti-blocking agents, pigments, fillers, lubricants, antistatic agents and antibacterial agents may be suitably added in the preparation of the resin composition. No special limitation is imposed on the mixing method. Thus, they can also be mixed with each other by a ribbon blender, a Henschel mixer or the like. This resin composition can be molded or formed and processed as it is or after pelleting. No particular limitation is imposed on the forming or forming method. By way of example, conventional processing methods used for thermoplastics, such as calendering, extrusion, blow molding and injection molding, can be adopted.

When the resin composition containing the graft copolymer and the thermoplastic resin is used as a transparent molded or formed product, the difference in refractive index between the grafted polymer and the graft copolymer is reduced and additionally the difference in the refractive index between the graft copolymer and the thermoplastic resin is It is desirable to adjust each composition so that it can be reduced. When transparency is considered important, it is preferable that the difference in refractive index between them is adjusted to 0.02 or less.

The present invention relates to a method for producing an expanded latex having a larger particle diameter by expanding the latex by agglomeration, and more particularly, a method for allowing the expansion of the latex while maintaining the stability of the latex, which is economical and productive. The present invention relates to a method for producing a graft copolymer using such expanded latex, a resin composition comprising a graft copolymer and a thermoplastic resin, and the like.

The invention will now be explained in more detail by the following examples and comparative examples. However, the present invention is not limited at all by this embodiment. Incidentally, the indications of "parts" and "%" used in the following examples mean parts by weight and% by weight unless otherwise indicated. In the Examples, the physical properties were measured according to the respective methods below.

(1) Volume average particle diameter and particle diameter distribution:

Electron micrographs obtained using a transmission type electron microscope were image analyzed with an image analyzer (manufactured by Asahi Chemical Industry Co., Ltd .; IP-500PC) to determine the volume average particle diameter (Dv; simply “average particle” of each sample). Also referred to as "diameter". The particle diameter distribution (Dv / Dn) was measured by calculating the ratio of the volume average particle diameter (Dv) to the number average particle diameter (Dn) obtained by analyzing the sample in the same manner as above.

(2) the refractive index of the enlarged latex forming component :

A cast film was formed by forming a cast film with each enlarged latex sample, and the resulting cast film was immersed in methyl alcohol and then vacuum dried at room temperature for 24 hours. The refractive index of the sample film was measured at 23 ° C. with an Abbe's refractometer.

(3) refractive index of graft copolymer and thermoplastic resin :

Each graft copolymer or thermoplastic resin sample was heat compressed at 200 ° C. to prepare a sample film. The refractive index of the sample film was measured at 23 ° C. with an Abbe refractometer.

(4) Impact strength of the molded product :

Toshiba Machine Co., Ltd. A specimen having a thickness of 3 mm or 6 mm was prepared using an injection molding machine IS-80 manufactured by the company. For these samples, impact strength was measured at 23 ° C or -10 ° C in JIS K 7110.

(5) Transparency of the molded product :

Each graft copolymer or thermoplastic resin composition sample was pelletized using an extruder and a pelletizer. The resulting pellet sample was heat compressed at 200 ° C. to prepare a sample plate having a thickness of 3 mm. For this sample plate, the transmittance and haze against parallel ray were measured at 23 ° C. using a scattering meter.

Example 1

1. Preparation of latex :

In pressure vessel with stirrer

Sodium chloride0.075part

Ferrous sulfate 0.005 parts

Disodium ethylenediaminetetraacetate 0.008 parts

Sodium formaldehyde sulfoxylate 0.05 parts

Benzalkonium chloride (cationic surfactant) 0.02 parts

Potassium oleate (anionic surfactant) 0.37 parts

200 parts of distilled water

After filling with, purifying with nitrogen,

Diisopropylbenzene hydroperoxide0.1part

Butadiene 75 parts

Styrene part 25

Was added. The polymerization was then carried out by keeping the contents at 60 ° C. for 15 hours, thus obtaining latex (A-1) having a conversion of 98% and a volume average particle diameter of 98 nm.

2. Expansion by flocculation :

While maintaining the obtained latex (A-1) at 70 ℃,

Sodium formaldehyde sulfoxylate (5% aqueous solution) 3.8 parts

Hydrogen peroxide (5% aqueous solution) 2.08 parts

Was added and the contents were stirred and mixed. Then stirring was stopped and the mixture was kept for 1 hour. Thereafter, 5 parts of sodium hydroxide (1% aqueous solution) was added, and the contents were stirred and mixed to obtain an expanded latex (B-1). Expanded latex (B-1) had a volume average particle diameter of 460 nm and a Dv / Dn of 1.38 and was mechanically stable. Incidentally, the total amount of precipitates and deposits on the polymerizer was 0.05% based on the packed monomers.

Example 2

1. Preparation of latex :

The polymerization was carried out in the same manner as in Example 1, except that 100 parts of butadiene were used instead of 75 parts of butadiene and 25% of styrene in the preparation of the latex of Example 1 to obtain a conversion rate of 98% and a volume average particle diameter of 92 nm. With latex (A-2) was obtained.

2. Expansion by flocculation :

The latex obtained in the same manner as in Example 1 except that 4.2 parts of sodium formaldehyde sulfoxylate (5% aqueous solution) and 2.32 parts of hydrogen peroxide (5% aqueous solution) were added to the latex (A-2). -2) was expanded by flocculation to give expanded latex (B-2). Expanded latex (B-2) had a volume average particle diameter of 500 nm and a Dv / Dn of 1.35 and was mechanically stable. Incidentally, the total amount of precipitate and deposits for the polymerization reactor was 0.07% based on the packed monomer.

Example 3

1. Preparation of latex :

Example 1 except in the preparation of the latex of Example 1 the amount of benzalkonium chloride (cationic surfactant) was increased from 0.02 parts to 0.05 parts and 100 parts butadiene was used instead of 75 parts butadiene and 25% styrene. The polymerization was carried out in the same manner as to obtain latex (A-3) having a conversion rate of 98% and a volume average particle diameter of 98 nm.

2. Expansion by flocculation :

The latex obtained in the same manner as in Example 1 except that 3.5 parts of sodium formaldehyde sulfoxylate (5% aqueous solution) and 1.9 parts of hydrogen peroxide (5% aqueous solution) were added to the latex (A-3). 3) was expanded by flocculation to give expanded latex (B-3). Expanded latex (B-3) had a volume average particle diameter of 250 nm and a Dv / Dn of 1.40 and was mechanically stable. Incidentally, the total amount of precipitate and deposits for the polymerization reactor was 0.04% based on the packed monomer.

Comparative Example 1

Expanded latex was obtained in the same manner as in Example 1 except that no benzalkonium chloride (cationic surfactant) was added in the preparation of the latex of Example 1. In the expansion step by flocculation, the expanded latex with an average particle diameter of 500 nm was obtained after maintaining the contents for 1 hour after stopping the agitation, but as soon as the agitation was started after the addition of sodium hydroxide for neutralization, the solids became agglomerates. It was precipitated and could not obtain a stable expanded latex.

Comparative Example 2

Instead of enlarging by aggregation, seed crystals were prepared by seed crystal polymerization method in order to carry out the production of latex having a large particle diameter. The latex (A-1) having a volume average particle diameter of 98 nm obtained in Example 1 was seeded. Used as particles.

Polymerization reactor

Sodium chloride0.075part

Ferrous sulfate 0.005 parts

Disodium ethylenediaminetetraacetate 0.008 parts

Sodium formaldehyde sulfoxylate 0.05 parts

Potassium oleate 0.37 parts

Latex (A-1) (in terms of solids) 1 part

200 parts of distilled water

After filling with nitrogen and purifying with nitrogen, the contents were kept at 60 ° C. and then

Butadiene 74.25 Part

Styrene 24.75 parts

Diisopropylbenzene hydroperoxide 1 part

Sodium formaldehyde sulfoxylate0.5part

Was added over 60 hours. The contents were then held at 60 ° C. for 30 hours. As a result, the volume average particle diameter expanded to 430 nm, but the conversion did not reach 95%.

Comparative Example 3

1. Preparation of latex :

Pressure vessel with stirrer

Tetrasodium pyrophosphate0.1part

Ferrous sulfate 0.005 parts

Disodium ethylenediaminetetraacetate 0.008 parts

Sodium formaldehyde sulfoxylate 0.05 parts

Potassium oleate 0.37 parts

200 parts of distilled water

Filled with nitrogen, purged with nitrogen,

Diisopropylbenzene hydroperoxide0.1part

Butadiene 75 parts

Styrene part 25

Was added. The contents were then maintained at 60 ° C. for 15 hours to yield latex (a-3) with a conversion of 98% and a volume average particle diameter of 97 nm.

2. Expansion by flocculation :

While maintaining the obtained latex (a-3) at 60 ° C., 0.2 part of disodium dodecyl phenyl ether disulfonate was added, and the rotation speed was decreased upon stirring. The expansion was carried out by aggregation by adding 1.2 parts of phosphoric acid (5% aqueous solution), but the latex solidified.

<Consideration>

Example 1 is an example where the present invention is applied to butadiene-styrene copolymer latex, and Examples 2 and 3 are examples where the present invention is applied to butadiene polymer latex. In either case, a stable expanded latex was obtained within a short time.

On the other hand, Comparative Example 1 is an example in which a cationic surfactant is not used when preparing butadiene-styrene copolymer latex. Also in the case of the comparative example 1, expansion by aggregation arises and advances. However, when the pH of the system is lowered, the restabilization effect by the cationic surfactant does not occur. Therefore, when sodium hydroxide was added to increase the pH of the system and thereby attempted stabilization of the system, solids precipitated due to the shear force by stirring, and failed to obtain a stable expanded latex.

Comparative Example 2 shows an example for obtaining a latex having the same particle diameter as in Example 1. It takes a very long time to carry out the polymerization. Thus, this embodiment is low productivity and not an economical way. Comparative Example 3 shows Example (A-2) described in Japanese Patent Application Laid-Open No. 71603/1998, which expanded the particle diameter to 260 nm, experimented without using an ionic surfactant, and obtained a larger particle diameter. The portion of phosphoric acid added was increased to obtain. However, latexes have generally solidified and as a result failed to obtain enlarged latexes.

Example 4

1. Graft Polymerization :

In pressure vessel with stirrer

Enlarged Latex (B-1) 75 parts (in terms of solids)

0.3 parts potassium oleate

Tetrasodium pyrophosphate 0.005 parts

After charging, heating to 60 ° C. and purifying with nitrogen,

Styrene Part 12.5

Methyl methacrylate 12.5 parts

Diisopropylbenzene hydroperoxide0.1part

Sodium formaldehyde sulfoxylate 0.05 parts

Was added over 1 hour. The contents were then held for 5 hours. As a result, a graft copolymer latex (C-4) having a volume average particle diameter of 480 nm and a Dv / Dn of 1.35 was obtained.

0.5 part of butylated hydroxy toluene (BHT) was added to this graft copolymer latex (C-4), followed by coagulation with 0.5% hydrochloric acid to wash the resulting coagulated product with water, dewatered and dried to obtain a powder graft copolymer. (D-4) was obtained. The refractive index of the polymer (B-1) grafted in this graft copolymer (D-4) was 1.539, and the refractive index of the graft copolymer (D-4) was 1.539.

Example 5

3.3 parts of sodium formaldehyde sulfoxylate (5% aqueous solution) and 1.8 parts of hydrogen peroxide (5% aqueous solution) were used in the expansion by aggregation of the latex (A-1) used to obtain the graft copolymer of Example 4 A graft copolymer latex (C-5) was obtained in the same manner as in Example 4 except that the graft copolymer (D-5) was recovered. Graft copolymer latex (C-5) had a volume average particle diameter of 205 nm and a Dv / Dn of 1.37. The refractive index of the polymer (B-5) grafted in this graft copolymer (D-5) was 1.539, and the refractive index of the graft copolymer (D-5) was 1.539.

Comparative Example 4

1.Expansion by flocculation :

While maintaining the latex (a-3) obtained in Comparative Example 3 at 60 ° C, 0.05 part of disodium dodecyl phenyl ether disulfonate was added, and then 56 parts of hydrochloric acid (0.15% aqueous solution) were added to increase the expansion by aggregation. Then, 10 parts of sodium hydroxide (1% aqueous solution) was added to give an expanded latex (b-4). This expanded latex (b-4) had a volume average particle diameter of 200 nm and a Dv / Dn of 1.90 and was mechanically stable. Incidentally, the total amount of precipitate and deposits for the polymerization reactor was 0.10% based on the packed monomer.

2. Graft Polymerization :

Graft polymerization was carried out in the same manner as in Example 4 using expanded latex (b-4) to give a graft copolymer latex (c-4) having a volume average particle diameter of 205 nm and a Dv / Dn of 1.85. , Powder graft copolymer (d-4) was obtained in the same manner as in Example 4. The refractive index of the polymer (b-4) grafted in this graft copolymer (d-4) was 1.539, and the refractive index of the graft copolymer (d-4) was 1.539.

<Physical Properties of Resin Composition>

Each of the graft copolymers obtained in Examples 4, 5 and Comparative Example 4 was used to prepare a resin composition containing a thermoplastic resin (MS resin) in accordance with the following formulation, and the physical properties thereof were measured. The refractive index of the MS resin used was 1.540.

Graft copolymer 30 parts

70 parts of MS resin (Denka TX-100, Denki Kagaku Kogyo Kabushiki Kaisha)

Toyo Seisaku-Sho, Ltd. Pelletized using a twin-screw conical extruder having a diameter of 20 mm manufactured by the company, and obtained pellets were obtained from Toshiba Machine Co., Ltd. The injection molding machine IS-80 manufactured by the company was molded into an impact test specimen having a thickness of 6 mm. Impact test was carried out at 23 ℃. The results are shown in Table 1.

Physical Properties of Thermoplastic Resin Composition (Based on MS Resin) Graft copolymer Impact Strength [KJ / m ² ] Transmittance for Parallel Radiation [%] Haze [%] Example 4 D-4 17.8 85 3.2 Example 5 D-5 5.8 90 1.7 Comparative Example 4 d-4 3.2 89 2.0

As shown in Table 1, the resin composition containing the graft copolymer (Example 4) having an enlarged particle diameter according to the present invention had a slight loss of transparency but was prepared using a conventional technique for expanding by aggregation. A great progress was made with respect to the impact strength compared to the resin composition containing the copolymer (Comparative Example 4). The resin composition using the graft copolymer (Example 5) according to the present invention, which has the same particle diameter as the resin composition in Comparative Example 4 and has a narrow particle diameter distribution, uses the graft copolymer of Comparative Example 4 Progress is shown in the balance between impact strength and transparency as compared to the resin composition.

Example 6

1. Graft Polymerization :

In pressure vessel with stirrer

Enlarged Latex (B-3) (parts solid) 75 parts

0.3 parts potassium oleate

Tetrasodium pyrophosphate 0.005 parts

After charging, heating to 60 ° C. and purifying with nitrogen,

Methyl methacrylate 12.5 parts

Butyl acrylate 2.5 parts

t-butyl hydroperoxide0.2part

Sodium formaldehyde sulfoxylate 0.2 parts

Was added over 1 hour. The contents are then held for 3 hours,

Styrene part 10

t-butyl hydroperoxide0.1part

Sodium formaldehyde sulfoxylate0.1part

Was added over 1 hour. The contents were then held for 5 hours to obtain graft copolymer latex (C-6) with a volume average particle diameter of 265 nm and a Dv / Dn of 1.37. Powder copolymer latex (D-6) was obtained from this graft copolymer latex (C-6) in the same manner as in Example 4.

Comparative Example 5

1. Preparation of latex :

In pressure vessel with stirrer

Tetrasodium pyrophosphate0.1part

Ferrous sulfate 0.005 parts

Disodium ethylenediaminetetraacetate 0.008 parts

Sodium formaldehyde sulfoxylate 0.05 parts

Disodium dodecyl phenyl ether disulfonate 0.02 parts

Potassium oleate 0.37 parts

200 parts of distilled water

Filled with nitrogen, purged with nitrogen,

Diisopropylbenzene hydroperoxide0.1part

Butadiene 100 parts

Was added. The contents were then held at 70 ° C. for 15 hours to give latex (a-5) with a conversion of 98% and a volume average particle diameter of 95 nm.

2. Expansion by flocculation :

While maintaining the obtained latex (a-5) at 60 ° C, 60 parts of hydrochloric acid (0.15% aqueous solution) was added to carry out enlargement by aggregation, and 10.7 parts of sodium hydroxide (1% aqueous solution) was added to enlarge latex (b- 5) was obtained. The expanded latex (b-5) had a volume average particle diameter of 220 nm and a Dv / Dn of 1.87 and was mechanically stable. Incidentally, the total amount of precipitate and deposits for the polymerization reactor was 0.12% based on the packed monomer.

3. Graft Polymerization :

Graft polymerization was carried out in the same manner as in Example 6 using expanded latex (b-5) to give a graft copolymer latex (c-5) having a volume average particle diameter of 225 nm and a Dv / Dn of 1.85. Powder graft copolymer (d-5) was obtained in the same manner as in Example 4.

<Physical Properties of Resin Composition>

Each graft copolymer obtained in Example 6 and Comparative Example 5 was used to prepare a resin composition containing a thermoplastic resin (vinyl chloride resin) in accordance with the following formulation, and its physical properties were measured. More specifically, the following mixing components were provided and filled in a Henschel mixer and heated to 115 ° C. under stirring to obtain a uniformly mixed resin composition.

Graft copolymer 9 parts

Vinyl chloride resin ("S9008", manufactured by Kureha Kagagu Kogyo K.K) 91 parts

Processing aid ("K130P", manufactured by Kureha Kagagu Kogyo K.K) 1.0 parts

Octyltin mercaptide ("KS2000A", manufactured by Kyodo Chemical Co., Ltd.) 1.8 parts

Calcium stearate ("Ca-St", manufactured by Nitto Kasei Co., Ltd.) 0.5part

Ester base lubricant ("SL-02", manufactured by Riken Vitamin Co., Ltd.) 0.6 parts

0.1 parts titanium oxide ("DP-3T-55", manufactured by Resino Color Industry Co., Ltd.)

Thereafter, the resin composition was changed to Toyo Seiki Seisaku-Sho, Ltd. Pelletizing was carried out using a twin-screw conical extruder having a diameter of 20 mm manufactured by Toshiba Machine Co., Ltd. The injection molding machine IS-80 manufactured by the company was used to mold the impact test specimen having a thickness of 3 mm. Impact tests were performed at 23 ° C and -10 ° C. The results are shown in Table 2.

Physical Properties of Thermoplastic Compositions (PVC Based) Graft copolymer Impact Strength (23 ℃) [KJ / m ² ] Impact Strength (-10 ℃) [KJ / m ² ] Example 6 D-6 116 41.0 Comparative Example 5 d-5 116 18.9

As shown in Table 2, the graft copolymer containing the graft copolymer according to the present invention (Example 6) exhibited the same impact strength at 23 ° C., but was prepared using conventional techniques for expansion by aggregation. A great progress was made with respect to the impact strength at a low temperature as compared with the resin composition containing the coalescence (Comparative Example 5).

In accordance with the present invention, there is provided a method of making enlarged latex, which method is economical and productive and allows for expanding the latex while retaining the stability of the latex. In the method for producing expanded latex according to the present invention, the stability of the latex is not impaired even when the polymerizable monomer is graft polymerized in the presence of the expanded latex.

According to the present invention, a process for producing a graft copolymer by polymerizing a monomer which can be polymerized in the presence of such an excellent and diverse property, such an expanded latex, a resin composition containing the graft copolymer and a thermoplastic resin Also provided are graft copolymers having a large particle diameter and a uniform particle diameter distribution. The resin composition according to the present invention is economically advanced in physical properties (particularly impact strength). Therefore, the present invention can be applied in various industrial fields where latex having a large particle diameter and graft copolymer having a large particle diameter are required.

Claims (27)

A process for preparing an expanded latex by expanding the latex by agglomeration, the method comprising: (1) (a) anionic surfactants and (b) at least one surfactant selected from the group consisting of cationic surfactants and amphoteric surfactants is present in the latex, (2) adding at least one selected from the group consisting of to the latex in the presence of the surfactant as a flocculating and expanding agent, (Iii) inorganic acids, (Ii) organic acids, (Iii) substances that form acids in water, (Iii) a combination of two or more substances that react with each other to form an acid, and (Iii) a substance that forms an acid by exposure to active rays, (3) The acid derived from the flocculating and expanding agent acts on the latex, thereby expanding the particle diameter of the latex. The method of claim 1 wherein the latex is a (co) polymer latex of diene monomer (s), a (co) polymer latex of vinyl monomer (s) or a copolymer latex of a diene monomer and a vinyl monomer. The method of claim 1, wherein at least one surfactant selected from the group consisting of (a) anionic surfactants and (b) cationic surfactants and amphoteric surfactants is used as surfactant in step (1) to provide monomer (s) To emulsion polymerization, whereby the surfactants (a) and (b) are present in the latex. The method of claim 1 wherein the anionic surfactant is a carboxylate type anionic surfactant. The process according to claim 1, wherein the cationic surfactant is a quaternary ammonium salt having at least one alkyl group, primary to tertiary amine salts having at least one alkyl group, alkylphosphonium salts or alkylsulfonium salts. The method of claim 1 wherein the amphoteric surfactant is betaine, a carboxylic acid type amphoteric surfactant comprising betaine, a sulfate type amphoteric surfactant or a sulfonic acid type amphoteric surfactant. The process according to claim 1, wherein in step (1), at least one surfactant selected from the group consisting of (b) cationic surfactants and amphoteric surfactants is contained in latex with (a) 0.01 to 100 moles per 100 moles of anionic surfactant. Manufacturing method to exist in proportion. A total weight of from 0.1 to 5 per 100 parts by weight of the (co) polymer component in the monomer (s) or latex in which the surfactants (a) and (b) form the (co) polymer component. A manufacturing method which makes it exist in a negative ratio. The process according to claim 1, wherein in step (2), a combination of two substances which perform an oxidation-reduction reaction to form an acid is used in combination of two or more substances which (i) react with each other to form an acid. 10. The process according to claim 9, wherein the combination of the two substances which undergo an oxidation-reduction reaction to form an acid is a combination of hydrogen peroxide and formaldehyde sulfoxylate. The process according to claim 1, wherein in step (3), the latex is expanded by brown agglomeration without performing agitation of the latex. The manufacturing method of Claim 1 which provides the expanded latex which has a volume average particle diameter of 150 nm or more by expansion by aggregation. The production method according to claim 1, wherein an expanded latex having a particle diameter distribution of 1.2 to 1.8, expressed as a ratio of volume average particle diameter (Dv) to number average particle diameter (Dn) (Dv / Dn), is obtained. Magnified latex obtained by the manufacturing method according to any one of claims 1 to 13. A process for preparing a graft copolymer comprising the polymerization of monomers which can be polymerized in the presence of expanded latex, wherein the expanded latex is obtained by a method comprising: (1) (a) anionic surfactants and (b) at least one surfactant selected from the group consisting of cationic surfactants and amphoteric surfactants is present in the latex, (2) adding at least one selected from the group consisting of to the latex in the presence of the surfactant as a flocculating and expanding agent, (Iii) inorganic acids, (Ii) organic acids, (Iii) substances that form acids in water, (Iii) a combination of two or more substances that react with each other to form an acid, and (Iii) a substance that forms an acid by exposure to actinic radiation, (3) The acid derived from the flocculating and expanding agent acts on the latex, thereby expanding the particle diameter of the latex. 16. The process of claim 15 wherein the monomer that can be polymerized is a vinyl monomer. The production method according to claim 15, wherein 95 to 5% by weight of the vinyl monomer is polymerized together with 5 to 95% by weight of the expanded latex in terms of a solid. The production method according to claim 15, wherein a graft copolymer having a particle diameter distribution of 1.2 to 1.8, expressed as the ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn), is obtained. The method of claim 15, wherein the difference in refractive index between the expanded latex and the graft copolymer particles formed is 0.02 or less. The production process according to claim 15, wherein a graft copolymer having a volume average particle diameter of 150 nm or more is obtained. Graft copolymer obtained by the manufacturing method according to any one of claims 15 to 20. A resin composition comprising the graft copolymer according to claim 21 and a thermoplastic resin. 23. The resin composition according to claim 22, which contains 0.1 to 99.9% by weight of the graft copolymer and 99.9 to 0.1% by weight of the thermoplastic resin. 23. The thermoplastic resin of claim 22 wherein the thermoplastic resin is polystyrene, high impact polystyrene, acrylic resin, methyl methacrylate-styrene resin, vinyl chloride resin, chlorinated vinyl chloride resin, acrylonitrile-styrene resin, acrylonitrile-butadiene A resin composition which is a styrene resin, a thermoplastic polyester resin, a polycarbonate resin or a mixture thereof. An anionic surfactant and at least one surfactant selected from the group consisting of cationic surfactants and amphoteric surfactants, the ratio of volume average particle diameter (Dv) to number average particle diameter (Dn) (Dv / Dn) A graft copolymer having a 1.2 to 1.8. The graft copolymer of claim 25, wherein the volume average particle diameter (Dv) is at least 150 nm. A resin composition comprising the graft copolymer according to claim 25 and a thermoplastic resin.